Ssystems and methods for self-optimization in wireless base stations by detection of interference at the edge of a received radio frequency band

Abstract

Systems and methods are described for reducing an interference level associated with frequency drift in a wireless base station. The base station monitors an interference level in a frequency resource caused by a first frequency resource colliding with a second frequency resource. If the interference level is outside of an expected range, the base station adjusts a parameter of the base station such as a reference oscillator frequency to compensate for frequency drift. This method may be used in a femtocell wireless base station.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application claims the benefit of U.S. Provisional Application No. 61 / 155,236, filed Feb. 25, 2009, which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The field of the present invention generally relates to systems and methods of self-optimizing radio access nodes that detect interference at the edge of the received radio frequency band. This optimization is intended to adjust a carrier frequency used by the radio access node to enhance network synchronization.BACKGROUND OF THE INVENTION[0003]In cellular networks, radio access base stations must use a very accurate time base as a reference for their frequency generation circuitry and other components. In order to achieve the required degree of accuracy, which is typically on the order of 0.05 parts per million (ppm), this reference must be even more accurate which thus requires specialized hardware. Various synchronization schemes include synchronizing with ...

AI Technical Summary

Benefits of technology

[0015]In accordance with another aspect of the present invention, adjusting the reference of the first base station reduces the interference level between the first frequency resource and the second frequency resource.

[0022]In accordance with another aspect of the present invention, adjusting the reference of the first base station reduces the interference level between the first frequency resource and the second frequency resource.

Problems solved by technology

The lack of a fixed line backhaul and extreme cost sensitivity of these femtocells require different synchronization schemes than larger cells use.

Additionally, traditional GPS synchronization may not work with femtocells as they are typically installed indoors where a GPS receiver cannot receive a signal from the GPS satellite system that is required to provide the high accuracy frequency reference.

But as network loading increases and creates more packet jitter and other errors such as packet loss, the derived synchronization error can increase and may cause the femtocell carrier frequency to exceed a specified error tolerance.

In one extreme case, the consumer IP network may be out of service completely and the timing packets would not be available to keep the femtocell adjusted properly.

However, these ovenized oscillators are relatively expensive and require calibration.

However, when a femtocell carrier frequency exceeds the specified error tolerance, a downlink transmission to a mobile device will be outside an allocated frequency range.

When this situation occurs it is an indication of carrier frequency error, and there will be significant interference in the received radio frequency band.

This approach has worked in large macrocell, microcell, and picocell radio access nodes, but does not scale well for use in a femtocell eNodeB base station.

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